This example project shows how to implement a custom CDI context with all the extras (including activation and deactivation). This branch uses CDI 4.1 and Weld 6.0.

Suppose we have a simple functional interface:

public interface Command {
    void execute();
}

Our mission is to provide a custom context so that it's possible to create bean instances whose lifecycle is bound to the command execution. In other words, a @CommandScoped bean instance should be destroyed after the execution completes. As a bonus we would like to be able to inject CommandExecution metadata (and see for example the time an execution started at).

First of all, we need to provide a scope annotation:

@NormalScope
public @interface CommandScoped {
}

Note that the scope is normal. This implies few facts and requirements:

• whenever you inject a @CommandScoped bean you get a client proxy, this allows e.g. to inject a @CommandScoped bean into @ApplicationScoped bean
• there may be no more than one mapped bean instance per @CommandScoped bean per thread

See also the spec - 6.3. Normal scopes and pseudo-scopes.

The other important class is CommandContextImpl. Few things to notice:

• ThreadLocal is used to store the map of bean instances
• there must be a way to activate/deactivate the context - see also activate() and deactivate() methods
• InjectableCommandContext is an injectable version of context which allow to detect the original "activator", so that it's possible to skip deactivation during deactivate()
• ContextualInstance wrapper allows to create and destroy a bean instance properly

The custom context can be activated/deactivated either by CommandDecorator, CommandExecutor or manually - a @Dependent bean with bean type CommandContext and qualifier @Default is automatically registered. See also the tests and compare the different ways of activating the context.

All the tests use Weld SE programmatic bootstrap API. This allows us to:

• run the tests as regular unit tests - no Java EE container is needed
• disable automatic discovery and gain the full control of scanning